pub fn heartbeat_path(root: &Path, project: &str, agent: &str) -> PathBufExpand description
Absolute path to the per-agent activity heartbeat marker (#428). The
PreToolUse/UserPromptSubmit hooks touch it on activity and the
Stop/StopFailure hooks rm it at turn-end; the TUI stats its
mtime at the 1s refresh and classifies the agent Working (touched
within 15s) or Idle. NOT JSON — a bare marker whose mtime is the whole
signal. Compound <project>-<agent> like every sibling helper, so
agents that share a name across projects never collide on one marker.